Global climate change, diet, and the complex relationship between human host and microbiome: Towards an integrated picture.

Dietary changes can alter the human microbiome with potential detrimental consequences for health. Given that environment, health, and evolution are interconnected, we ask: Could diet-driven microbiome perturbations have consequences that extend beyond their immediate impact on human health? We address this question in the context of the urgent health challenges posed by global climate change. Drawing on recent studies, we propose that not only can diet-driven microbiome changes lead to dysbiosis, they can also shape life-history traits and fuel human evolution. We posit that dietary shifts prompt mismatched microbiome-host genetics configurations that modulate human longevity and reproductive success. These mismatches can also induce a heritable intra-holobiont stress response, which encourages the holobiont to re-establish equilibrium within the changed nutritional environment. Thus, while mismatches between climate change-related genetic and epigenetic configurations within the holobiont increase the risk and severity of diseases, they may also affect life-history traits and facilitate adaptive responses. These propositions form a framework that can help systematize and address climate-related dietary challenges for policy and health interventions.

What's Wrong with Evolutionary Causation?

This review essay reflects on recent discussions in evolutionary biology and philosophy of science on the central causes of evolution and the structure of causal explanations in evolutionary theory. In this debate, it has been argued that our view of evolutionary causation should be rethought by including more seriously developmental causes and causes of the individual acting organism. I use Tobias Uller's and Kevin Laland's volume Evolutionary Causation as well as recent reviews of it as a starting point to reflect on the causal role of agency, individuality, and the environment in evolution. In addition, I critically discuss classical philosophical frameworks of theory change (i.e. Popper's, Kuhn's and Lakatos') used in this debate to understand changing views of evolutionary causation.

The holobiont concept before Margulis.

In recent years, Lynn Margulis has been credited in various articles as the person who introduced the concept of holobiont into biology in the early 1990s. Today, the origin of evolutionary studies on holobionts is closely linked to her name. However, Margulis was not the first person to use this concept in its current context. That honor goes to the German theoretical biologist Adolf Meyer-Abich, who introduced the holobiont concept nearly 50 years before her (in 1943). Although nearly completely forgotten today, in the 1940-60s he developed a comprehensive theory of evolutionary change through "holobiosis." It had a surprisingly modern outlook, as it not only addressed tenets of today's evolutionary developmental biology (evo-devo), like the origin of form and production of variation, but also anticipated key elements of Margulis' later endosymbiotic theory. As the holobiont concept has become an important guiding concept for organizing research, labeling conferences, and publishing articles on host-microbiota collectives and hologenomes, the field should become aware of the independent origin of this concept in the context of holistic biology of the 1940s.

Publisher Correction to: O Organism, Where Art Thou? Old and New Challenges for Organism-Centered Biology.

Please note that this article belongs to the Special Issue on "New Styles of Thought and Practices: Biology in the Interwar Period," guest editors Jan Baedke and Christina Brandt, but was included in volume 52, issue 2, Summer 2019 by mistake. It should be regarded as part of this special issue collection of articles.

O Organism, Where Art Thou? Old and New Challenges for Organism-Centered Biology.

This paper addresses theoretical challenges, still relevant today, that arose in the first decades of the twentieth century related to the concept of the organism. During this period, new insights into the plasticity and robustness of organisms as well as their complex interactions fueled calls, especially in the UK and in the German-speaking world, for grounding biological theory on the concept of the organism. This new organism-centered biology (OCB) understood organisms as the most important explanatory and methodological unit in biological investigations. At least three theoretical strands can be distinguished in this movement: Organicism, dialectical materialism, and (German) holistic biology. This paper shows that a major challenge of OCB was to describe the individual organism as a causally autonomous and discrete unit with consistent boundaries and, at the same time, as inextricably interwoven with its environment. In other words, OCB had to conciliate individualistic with anti-individualistic perspectives. This challenge was addressed by developing a concept of life that included functionalist and metabolic elements, as well as biochemical and physical ones. It allowed for specifying organisms as life forms that actively delimit themselves from the environment. Finally, this paper shows that the recent return to the concept of the organism, especially in the so-called "Extended Evolutionary Synthesis," is challenged by similar anti-individualistic tendencies. However, in contrast to its early-twentieth-century forerunner, today's organism-centered approaches have not yet offered a solution to this problem.

Race and nutrition in the New World: Colonial shadows in the age of epigenetics.

This paper addresses historical dimensions of epigenetic studies on human populations. We show that postgenomic research on health disparities in Latin America reintroduces old colonial views about the relations between race, environment, and social status. This especially refers to the idea - common in colonial humoralism and epigenetics - that different types of bodies are in balance and closely linked with particular local environments and lifestyles. These social differences become embodied as physiological and health differences. By comparing Spanish chronicles of the New World with recent epidemiological narratives on Mexican populations in social epigenetics (especially on obesity), we identify four characteristics that both share in distinguishing races, such as indigenous or mestizos from Spaniards or non-Mexicans: (i) Race is not intrinsic to bodies but emerges as a particular homeostatic body-environment relation; (ii) the stability of one's race is warranted through the stability of one's local environment and lifestyle, especially nutrition; (iii) every race faces specific life challenges in a local environment to maintain its health; and (iv) every race shows a unique social status that is closely linked to its biological status (e.g., disease susceptibility). Based on these similarities, we argue that currently in Latin America the field of epigenetics appears on the scene with a worrisome colonial shadow. It reintroduces long forgotten exclusionary and stereotypic perspectives on indigenous and mestizos, and biologizes as well as racializes social-cultural differences among human groups.

From seconds to eons: Time scales, hierarchies, and processes in evo-devo.

This paper addresses the role of time scales in conceptualizing biological hierarchies. So far, the concept of hierarchies in philosophy of science has been dominated by the idea of composition and parthood, respectively. However, this view does not exhaust the diversity of hierarchical descriptions in the biosciences. Therefore, we highlight a type of hierarchy usually overlooked by philosophers of science. It distinguishes processes based on the different time scales (i.e. rates, frequencies, and rhythms) on which they occur. These time scale hierarchies often are connected with assumptions defended in process ontology. Due to their ability to describe interlevel dynamics of various kinds, we call these hierarchies 'dynamic hierarchies.' In order to highlight and discuss their organization, explanatory roles, and epistemic virtues we focus on dynamic hierarchies in developmental biology and evolutionary developmental biology (evo-devo). In these fields, dynamic hierarchies offer crucial complementary information to descriptions of compositional hierarchies.

Model organisms in evo-devo: promises and pitfalls of the comparative approach.

Evolutionary developmental biology (evo-devo) is a rapidly growing discipline whose ambition is to address questions that are of relevance to both evolutionary biology and developmental biology. This field has been increasingly progressing as a new and independent comparative science. However, we argue that evo-devo's comparative approach is challenged by several metaphysical, methodological and socio-disciplinary issues related to the foundation of heuristic functions of model organisms and the possible criteria to be adopted for their selection. In addition, new tools have to be developed to deal with newly chosen model organisms. Therefore, we present a modelling framework suitable to integrate data on individual variation into evo-devo studies on new model organisms and thus to compensate for current idealization practices deliberately suppressing variation.

The epigenetic landscape in the course of time: Conrad Hal Waddington's methodological impact on the life sciences.

It seems that the reception of Conrad Hal Waddington's work never really gathered speed in mainstream biology. This paper, offering a transdisciplinary survey of approaches using his epigenetic landscape images, argues that (i) Waddington's legacy is much broader than is usually recognized--it is widespread across the life sciences (e.g. stem cell biology, developmental psychology and cultural anthropology). In addition, I will show that (ii) there exist as yet unrecognized heuristic roles, especially in model building and theory formation, which Waddington's images play within his work. These different methodological facets envisioned by Waddington are used as a natural framework to analyze and classify the manners of usage of epigenetic landscape images in post-Waddingtonian 'landscape approaches'. This evaluation of Waddington's pictorial legacy reveals that there are highly diverse lines of traditions in the life sciences, which are deeply rooted in Waddington's methodological work.